93de2891fa9cb8314573ba3a6ab764bc9c52444d wallet: assert to ensure accuracy of CMerkleTx::GetBlocksToMaturity (Ben Woosley)
Pull request description:
According to my understanding, it should not be possible for coinbase
transactions to be conflicting, thus it should not be possible for
GetDepthInMainChain to return a negative result. If it did, this would
also result in innacurate results for GetBlocksToMaturity due to the
math therein. asserting ensures accuracy.
https://github.com/bitcoin/bitcoin/pull/13657/commits/93de2891fa9cb8314573ba3a6ab764bc9c52444d
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Backport of Core PR13657